SEATTLE - Police dismantled a tent on Monday used as a staging area for protests in Seattle over Royal Dutch Shell Plc’s use of the city’s port as a home base for a drilling rig that could depart this week for the Arctic. Over the last month, activists have staged demonstrations against the oil company’s Arctic drilling plans, including on May 16 when hundreds of protesters in kayaks and small boats fanned out on a Seattle bay. Seattle police dismantled but did not seize the 16-foot (5-meter) by 32-foot (10-meter) logistics tent central to organizing the launch of a planned rig-stopping flotilla, said Backbone Campaign Executive Director Bill Moyer. He said discussions with the U.S. Coast Guard suggest the Polar Pioneer rig could begin its voyage to Alaska this week, possibly on Wednesday, though neither Shell nor shipping company Foss Maritime has commented publicly on the schedule. Environmental groups say drilling in the Chukchi Sea off Alaska could lead to an ecological catastrophe. “We would like Seattle to mobilize as many craft on the water as possible to be a flotilla through which this rig is not allowed to attempt to pass through,” Moyer said. Seattle Police Department spokesman Drew Fowler said the tent was taken down in a West Seattle park that doubles as a boat launch and returned to its owner, though he was not sure whether Seattle or parks officers dismantled it. “Folks had been camping in the tent, which is not allowed in any Seattle park,” Fowler said. There were no arrests. Activists say they want to get boats on the water as soon as they learn the rig is leaving the terminal. A mandatory safety zone keeping watercraft at least 100 yards away from the rig will expand to 500 yards when it hits the broader Puget Sound on its way to Alaska. Activists are asking people to sign up for protest shifts so they can be called upon to quickly mobilize when the rig prepares for departure. The Coast Guard will enforce the safety zone in the Puget Sound, spokesman George Degener said, adding that it can be “almost impossible” for the rig to stop if a boat were to suddenly enter its immediate path. Shell did not immediately respond to a request for comment, nor did Foss Maritime.